Transmission regulating system



Aug. 30, 1932.. w H, HOLDEN 1,874,530

TRANSMISSION REGULATING SYSTEM Filed Dec. 26, 1931 INVENTOR ATTORNEY systems,

Patented Aug. 30; 1932 UNITED STATES PATENT OFFICE WILLIAM H; T. HOLDEN,

OF BROOKLYN, NEW YORK, ASSIG-NOR TO AMERICAN TELE- TRANSMISSION REGULATING SYSTEM Application filed. December 26, 1931. Serial No. 583,381.

This invention relates to transmission and more particularly to means for regulating transmission on the lines of such systems. I

In telephone or telegraph transmission systems, particularly of the carrier type, it may be desirable to automatically regulate the transmission over lines of such systems so that the current at the end of the line will be of constant output or of an output between desired levels. This has been accomplished by transmitting a pilot channel over a line and utilizing increases or decreases in said pilot channel to cut in or out of the line elements of networks or artificial lines to regulate transmission to keep the output between desired levels. The means for switching in and out of the line the elements of these networks have heretofore been relays. In such systems, particularly those utilizing a number of carrier channels, it is necessary to effect very dependable operation ofthese relays as their contacts may be directly in the transmission circuit. Accordingly, careful attention to their mechanical adjustment has been necessary. The arrangements of the invention provide a means for automatically controlling the transmission in a line by means of a pilot channel without the use of relays and hence afiord the particular advantage of providing a device which eliminates mechanical moving parts in such a system.

In a copending application filed in the name of Charles S. Demarest, Serial No. 574,207, is shown an arrangement wherein a pilot channel current is transmitted through the variable network or artificial line to the receiving circuit with the desired volume as determined by the number of pads or elements of the artificial lines which may be connected in the circuit. The connection of these pads or elements to the line is controlled by switching units employing gasfiled thermionic tubes to perform the functions heretofore performedby relays. The arrangement is such that thenumber of pads or elements of the artificial lines to be cut into the circuit will be dependent upon the voltage of the received pilot channel current. The arrangements of the present invention provide in a system of the above type improved arrangements for controlling the operation of the switching units employing gas-filled tubes and more particularly to improved arrangements for controlling the sequential operation of these switching units. ther objects and features of the invention will appear more fully from the detailed description thereof hereinafter given.

The invention may be more fully understood from the following description, together with the accompanying drawing in the Figures 1 and 2 of which the invention is illustrated. In Fig. 1 is shown a circuit diagram illustrating a switching unit of the invention for cutting in or out of a line an artificial line having a single set of pads or elements. In Fig. 2 is shown a circuit diagram illustrating a plurality of switching units of the invention and means for operating them sequentially to cut in or out of the line a number of artificial lines. Similar reference characters have been utilized to denote like parts in both figures.

In the drawing is shown a transmission line L in which it may be automatically desired to regulate transmission by means, for example, of a pilot channel current transmitted over the line. will be included in the line L an artificial line or network N This network would comprise series and shunt elements. The series element 4 would comprise inductance and resistance. The shunt element 5 would comprise a circuit including inductance and resistance. Networks of this type are well known in the art. The connection in the line L of the series and shunt elements of the network N is controlled by a switching unit comprising the gas-filled thermionic tubes G and G These gas-filled tubes have the characteristic that when the input voltage applied to the grids is of a certain value, the tubes will operate and an arc of relatively low resistance will be formed between the cathode and plate elements of the tubes. Obviously, when the tubes are in a non-operative condition and no low resistance are exists, the resistance between cathode and Accordingly, there will be included in the line. When thetube G operates and a low resistance are is,

plate is very high. When the tube G discharges and a low resistance are is formed in the cathodeplate circuit thereof, the cathode-plate circuit of the tube will close a shunt about the series element 4 of the network N When the tube G is in anono erative condition the shunt circuit Wlll be e ectively opened and the series element 4 formed in the cathode-plate circuit of this tube, the cathode-plate circuit will connect the shunt element 5 of the network N across the two sides of the line L When the tube G is in a non-operative condition its plate .circuit willbeefliectively opened and the .Shunt element 5 will not be connected across battery supply circuit for the cathode plate circuit of tube G would be completed from the ground 13, cathode and plate elements of 7 tube G to the battery 3 and ground 12. The

operating voltages for the grids of the tubes .G andG will be obtained from a circuit including the rectifyin tube V whose in-' put will be connected throughthe selective circuits 2 and 1 across the line L A plurality of condensers such as C and inductances such as L have been illustrated. In

all cases these elements are to separate the battery plate circuits for the tubes from the transmission path. v

The. operation of the arrangement of Fig. 1 is as follows: A pilot channel current will be transmitted overthe' line L and thence over the selective circuits 1 and 2 to the input circuit of the rectifying tube V The plate circuit of tubs V includes the plate battery E and the resistance elements R and R. It is also connected to the batteries E and E which supply voltage to the grids of tubes G2 and G respectively. If the equivalent of line L is within desired limits, the ilotcurrent in the input circuit of the tube Q will be of a normal value. This will produce a current flow in the output circuit of this tube through the resistances R and R. The current flowing through the resistance R will produce a voltage drop across said resistance which will be subtracted from the voltage drop of the battery E and the current flowing through the resistance R will produce a voltage drop which will be added to the voltage of the battery E l/Vhenthe pilot current is of normal value, the voltage on the grid of the tube G due to the voltage of the battery E augmented by the voltage drop across resistance R is of a negative value small enough so that the tube G will discharge. Also, under these conditions, the voltage on the grid of tube G due to the voltage of the battery E decreased by the small drop in resistance R will be of a negative value sufficiently large so'that the tube G will be blocked. Under these conditions the plate circuit of the tube G will effectively close a short-circuitabout the series celement l of network Ni and the plate circuit of I the tube G will open the circuit across line L ywhich includes the shunt element 5 of the network N In other words, when the pilot current is of normal value the network N will be disconnected from the line L If the equivalent of line L shouldnow change so that the pilot current in the input of the tube V should increase, an increase, in the current flowing through the resistance R will take place. Accordingly,- the negative voltage applied to the grid oftube G from the'battery E will be decreased by a greater potential drop in resistance R. In other words,the negative potential on the grid of tube G will be so reduced that this tube will now discharge. The increase in the current in the plate circuit of tube V will at the same time increase the potential drop across the resistance R. This will further increase the voltage supplied to the grid of tube G by the battery E to such a point where the tube Gr would notbreak down if it had not'been operated. The tube G however, would not be stopped from its operating condition by this increase in the negative voltage applied to its grid because it has the characteristic that when once broken down, it will discharge regardless of the grid voltage. The break-down and operation of the tube G: will cause a current to flow in the plate circuit of this tube. As has been pointed out, this plate circuit is connected by conductor 11 to a point P of a circuit including a combination of capacity C and inductance L Due to the action of the circuit 6 when the current begins to flow in the plate circuit of the tube G the potential at point P in said circuit will be lowered. The lowering of the potential at point P will reduce across the sides of the line L for the shunt element 5 of the network. The deenergization of the tube G will open the short circuit about theseri'es element 4 of the network hl and accordingly, the network N will be included in the line when the pilot current increases.

over the line L will now be decreased by the 'lOO The pilot current coming into the tube V inclusion in the line of the network N If the pilot current is sufli'ciently decreased by the inclusion in the line of the network the pilot level and hence the plate current of V will be within normal limits. If a change in line equivalent causes further reduction of the pilot channel, the voltage on the grid of tube G will be reduced 'to the point where said tube will breakdownand operate. This will cause a current to flow in the plate circuitof sa'idtube, which-circuit has been pointed out as connected to the point P of the circuit arrangement 6. Due to the action of thecircuit 6 when current begins to flow in the plate circuit of tube G the potential at point P will be lowered. The lowering of the potential at point P will stop the flow of current in the plate circuit of the tube G "artificial lines or networksN The tube G will 'then'cease -to function because the negative potential impressed on its gridhas been sufficiently increased by the decrease in the pilot current. Under such "conditions the elements of the network N compensate for changes in the line equivalent.

Similar reference characters have been used in Fig. 2 to denote like parts with respect'to Fig. 1. Associated with'the line L would be the networks N and N Thenetwork N 'would have series and shunt elements 4 and -'5 adapted tobe'con nected to or disconnected from theline by the cathode plate circuits of'the gas-filledtubes G and G in a manner similar to the arrangements of 1. The network N 'would have series and shu'nt elements-27 and 28 adapted to be connected to or disconnected from the line in'a'similar'manner bythe cathode plate circuits ofJthe gas-fill'ed tubes G and G The operation of these gas-filled tubes are controlled by the action of the gas-filled tubes G -andG which in turn are controlled by the currents in the plate circuit of theidetector tube V The detector tube V is connected to the line, as'in Fig. 1, by the tuned circuits land 2 and is operatedby'thepilot channel 7 currents transmitted over the line.

The arrangements of Fig. 2 may be more fully understood from the description of their operatiomwhich is as follows:

The pilot current transmitted overline L will be transmitted over the selective circuits 1 and 2 and appliedto the detector tube V and will control the flow of current in the plate circuit of tube V and hence the potential drop in-the resistancesR' and R. lVhen the level of the pilot currentis within normal limits the potential drop in resistances'R and p R combined'with'the voltages of batteries E '65 and E willproduce a potential on the grids of tubes G and G such that these tubes will not break down and operate.

An increase in the pilot current-will increase the potential drop in resistance R and, as this drop is subtracted from the voltage of battery E the negative voltage applied to the grid of tube GB will be so reduced that the tube will break down and operate. The plate circuit of tube G is completed over a winding of transformer T and battery 15 to ground. Connected to another winding of transformer T is a circuit including a source 16 of alternating current. This alternating current source 16 may be used for quenching the arc in tube G when the grid voltage becomes more negative than the critical value. When the tube G breaks down and operates the alternating current from source'16 is applied through transformers T and T and T to the grids of tubes G and G On the other 1 hand if the pilot current decreases beyond its normal level a decrease will take place inthe potential drop in resistance R and; as this drop is added to the voltage of battery E 'thegnegative voltage applied to the grid of tube G will he reduced that the tube will break down and operate. It is pointed out that this reduction in the pilot current will at the same time in crease the negative potential applied to the grid of tube G beyond-the critical value and it will cease to operate. When the tube G operates alternating current from the source 16 will be applied thorugh transformers T T and T to the grids of tubes G and G Thus it will be seen that an increase or decrease in the pilot current will cause one of the tubes G or G to operate and the other to be extinguished. Also the operation of one of said tubes will cause an alternatin current potential to be applied-to the grids of-tubes G and Gr and the operation of the other of said tubes'will cause an alternating current potential to be applied to the grids of tubes G and G In a manner similar to that heretofore pointed out with respect to Fig. 1 when tubes Gr and G are operated and tubes G and Gr are not operated the networks N and N will be cut out of the line. If under the above conditions the pilot current increases, an alternating current potential will be applied to the grids of tubes and G in the manner heretofore pointed out. This alternating current potential will now operate'tube G but will not operate tube G as tube G has a higher ne ative grid potential normally applied thereto, the grid potential of G being that of battery E and the grid potential of G being that of battery E and plus battery E The operation of tube G will connect the shunt element 5 of network 1 1 across 'line L The operation of tube G5 will due to circuit 6 cause tube G to be extinguished in a manner similar to that pointed out with respect. to Fig. 1. The extinguishing of tube 1G will open the short circuit around element 4 and allow this element to be connected in thefline'. Thus the network N will be cut into the line."

The operation of tubeGr will cause a current to flow through resistance 14. The potential drop in this resistance l4-will com- The tube G4, howevenwill not necessarily pensate for the voltage of battery E In other words, the voltage drop of resistance 14 will reduce the negative vintage applied to the grid of tube Gr so that it will now be the same as that applied to the grid of tube G operate at this time because the cutting in of the network N has so reduced the pilot .current that tube GB will not be operated. I If the level of the'pilot current increases even with network N in the line to the point where tube GB again operates, then the alternatlng potential applied to tube G1; will cause it tooperate. Ina manner similar to that heretofore described the operation of tube G; will deenergize tube G and the'network N ewill' be cut into the line.

I If,'with both the networks and N out into the line, the level of the pilot current now "decreases the tube G will be operated and an alternating current potential will be applied to the grids of tubes G and G, as heretofore pointed out. The grid of tube G normally has a higher negative volt-age applied thereto'than the grid of tube G5, the

voltage on G being that of batteries E and E and the voltage on G being that of battery E Accordingly, the alternating potential applied to the tubeswill operate tube The-operation of G will close a 7 short circuit about element 27 and in a mannersimilar to that heretofore described will through circuit 21 deenergize tube G This will disconnect the networkN from the line. When the tube'Gr operates a current will flow through the resistance 23 and cause a potential' drop. therein which will compensate for the voltage of battery E In other words the voltage drop in resistance 23 will reduce thevoltage applied to the grid of tube G to the same level as that applied to the'g'rid of tube G The tube G however, will not necessarily operate at this time be cause the cutting out of the network N has ,will not' be operated.

so increased the pilot current that tube G If the pilot current continuesto decrcase'even with network N out out of the line to the point wl 'e tube again. operates, then the alterng current applied to the "grid of tube Gr will cause it to operate. This will cause the deenergi'zation of tube G and will cut out of the line the network N While the line has been shown with only two artificial lines or networks connected thereto,it is pointed out that additional artiv -ficial lines might be provided together with additional switching unitssimilar to those shown forconnecting said artificial lines to the transmission line, Accordingly, while the arrangements of the invention have been shown as embodied in certain specific forms which are deemed desirable, it is understood that they are capable of embodiment in many and other widely varied forms without departing from the spirit of the invention as defined by the appended claims.

What is claimed is: I I

I. A transmission line, a network com rising an element adapted to be connecte in series in said line and an element adapted to be connectedin shunt in said line, two as filled thermionic. tubes, means for comp eting the circuit for said shunt element over the cathode plate circuit of the first of said tubes,

a short circuit about said series element com-' pleted over the cathode plate circuit of the second of said tubes, means controlled by the operation of eitherone of said'tubes for deenergizing the other of said tubes, and means controlled byv the Volta e of currents transmitted over said line or operatin one of said tubes and-for supplying aibloc ing potential for the grid oftheoth'er of saidtubes.

2. A. transmission line, a network comprising an element adapted to be connected in series in said line and anelement adapted to be connected in shunt in said line, two gas filled thermionic tubes, means forQCOmpletmg the circuit; forv said shunt element over .theqcathode plate circuitof the firstofsaid tubes,ra shortcircuitabout'said series elementcompleted *overthe cathode plate circuit of. the second of said tubes, means 'controlled by the operation of either one of said tubes for deenergizing the other of said tubes, and means controlled by an increase in the voltageofv currents transmitted over said line for supplying. an operating potential for the grid of the first of said tubes and a .blocki potential'for'the grid of thesecond of sai tubes and controlled by a decreasein the. voltage of currents transmitted'over said line for supplying a blocking potential fox-the grid of the first of said" tubes and an operating potential for the grid ofthe second of said tubes. 1 a i i i 3. A transmission line overwhicha pilot current is transmitted,a network comprising an element adaptedto be connected in series in said line and an element adapted to be current is transmitted, a network comprising an element adapted to be connected in series in said line and an element adapted to be connected in shunt in said line, two gas filled thermionic tubes, means for completing the circuit for said shunt element over the cathode plate circuit of the first of said tubes, a short circuit about said series element completed over the cathode plate circuit of the second of said tubes, means controlled by the operation of either one of said tubes for deenergizing the other of said tubes, a rectifier connected across said line by a circuit selective for said pilot current, resistance elements in the plate circuit of said rectifier, and battery supply circuits for the grids of said thermionic tubes connected to said resistance elements whereby the potential drop in said resistance elements may supplement the vol ages of said battery supply circuits.

5. A transmission line over which a pilot current is transmitted, a network comprising an element adapted to be connec ed in series in said line and an element adapted to be connected in shunt in said line, two gas filled thermionic tubes, means for completing the circuit for said shunt element over the cathode plate circuit of the first of said 'tubes, a short circuit about said series element completed over the cathode plate circuit of the second of said tubes. means controlled by the operation of either one of said tubes for deenergizing the other of said tubes, a rectifier connected across said line by a circuit selective for said pilot current, two resistance elements in the plate circuit of said rectifier, and battery supply circuits for the grids of said thermionic tubes, the battery supply circuit for said first tube being so connected to one of said resistances that the potential drop therein due to the rectified currents will be subtracted from the voltage of said battery supply circuit, the battery supply circuit for said second tube being so connected to the other of said resistances that the potential drop therein due to the rectified currents will be added to the voltage of said battery supply circuit.

6. A transmission line over which a pilot current is transmitted, a network, a switching unit for connecting said network in said line, a rectifier connected across said line by a circuit selective for said pilot current, two gas filled thermionic tubes connected to the plate circuit of said rectifier, means controlled by voltages in the plate circuit of said rectifier for operating either of said thermionic tubes, and means controlled by said tubes for operating said switching unit.

7. A transmission line over which a pilot current is transmitted, a plurality of networks, a plurality'otswitching units for connecting said networks in said line, a rectifier connected across said line by a circuit selective for said pilot current, two gas filled tubes connected to the plate circuit of said-recti fier, means controlled by an initial variation in voltage-in the plate circuit of said rectifier forcausing the initial operation of one of said tubes, means controlled by the initial operation of one of said tubes for operating one of said switching units, means controlled by the operationof said switching unit for releasing said operated tube, means controlled by a. subsequent variation in voltage inthe.

plate circuit or" said rectifier for causing the subsequent operation of one of said tubes, and means controlled by the subsequent operation of one of said tubes for operating another of said switching units.

8. A transmission line over which a pilot current is transmitted, a network, a, switching unit for connecting said network in said line, a rectifier connected across said line by a circuit selective for said pilot current, two resistance elements in the plate circuit of said rectifier, two gas filled thermionic control tubes, battery supply circuits for the grids of said control tubes, the battery supply circuit for the grid of said first control tube being so connected to one of said resistances that the potential drop therein due to the rectified currents will be subtracted from the voltage of said battery supply circuit and the battery supply circuit for the grid of the other of said control tubes being so connected to the other of said resistances that the potential drop therein due to the rectified currents will be added to the voltage of said battery supply circuit, said switching unit comprising two gas filled thermionic tubes and means whereby the cathode plate circuits of said tubes will control connection in said line of the elements of said network, and means controlled by the operation of said control tubes for applying potentials to the tubes of said switching unit to control their energization.

9. A transmission line over which a pilot current is transmitted, a plurality of networks, each of said networks comprising elements adapted to be connected in series in said line and elements adapted to be connected in shunt in said line, a plurality of switching units for controlling the connection of said networks in said line, each of said switching units comprising two gas filled thermionic tubes, the cathode plate circuits of first of the tubes of each unit controlling the connection in the line of the series elements of said networks, the cathode plate circuits of the second of the tubes of each unit controlling the connection in the line of the shunt elements of said networks, battery supply circuits for the grids of the first set of tubes controlling said series elements,

batte supply circuits for the grids of the secon set of tubes controlling'said shunt elements, said first mentioned battery supply circuit being adjusted so that when none of the first set of tubes are operated the negative voltage applied 'by the batter supply circuit to one tube will be less t an that applied to the preceding tube and when said one tube is operated the negative voltage applied by the battery supply circuit to the preceding tube will be reduced, said second mentioned battery supply circuit being adjusted so that when none of the second set i of tubes are operated the negative voltage applied by the battery supply circuit to one tube will be less than that applied to the v succeeding tube and when said one tube is operated the negative voltage applied by the battery supplycircuit to the succeeding tube will'be reduced, and means controlled bythe voltages of the pilot current transmitted over said lme for applying voltages to the grids of either of said sets of tubes.

In'testimony whereof, I have signed my December, 1931. i

' WILLIAM H. T. HOLDEN.

name to this specification this 23rd day of 

